1. Field of the Invention
The present invention relates to a bearing device for motors and, in particular, a bearing device comprising a plurality of bearings made of different materials.
2. Description of the Prior Art
A bearing for a fan motor is usually fixed in a stator. A shaft attached to a rotor is rotatably received in the bearing. In earlier days, a ball bearing was the preferred kind of bearing. However, ball bearings are noisy and relatively expensive. To overcome these shortcomings, a kind of self-lubricating bearing made of metallic material has been developed. As shown in FIG. 7, a conventional motor 1 includes a rotor 2, a shaft 3, a self-lubricating bearing 4, a bearing sleeve 5, a stator 6 and a locking fastener 7. The stator 6 is fixed around the bearing sleeve 5. The self-lubricating bearing 4 is tightly fixed within the bearing sleeve 5. One end of the shaft 3 is fixed in a center of the rotor 2, and the other end accommodates the locking fastener 7. The shaft 3 is rotatably received in a central hole 8 of the bearing 4. However, the bearing 4 has low durability. To overcome this shortcoming, a kind of ceramic material bearing has been developed. However, the ceramic material bearing cannot self-lubricate.
Accordingly, an object of the present invention is to provide a self-lubricating bearing device which is durable and not noisy.
To achieve the above-mentioned object, a bearing device of the present invention used in a motor includes a bearing set and a shaft. A preferred embodiment of the bearing set comprises a first bearing and a second bearing. The first and second bearings are made of different materials. In the preferred embodiment, the materials are sintered metallic material and ceramic material respectively. An annular recess is defined in one end of the first bearing. The second bearing is received in the recess of the first bearing. Each bearing defines a central hole. The central holes of the first and second bearings have a same diameter. A guiding head is formed at one end of the shaft. The motor comprises a rotor, a stator, and a bearing sleeve. In assembly, one end of the shaft is fixed in a center of the rotor. The second bearing is inserted into the recess of the first bearing. The bearing set is fixed within the bearing sleeve. The stator is fixed around the bearing sleeve. The shaft is rotatably received in the central holes of the bearings. During operation, the shaft rotates smoothly and stably in the bearing set.
Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: